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    <title>Document</title>
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<script>
    var arr = [1,2,3,4,5,6,7]
    function arrFn(ars){
        // forEach()//没有返回值 没有返回值 没有返回值 return没有用！！！！！！！！！！！
        // return arr.every(item=>item == ars) //全部为真 返回true
        for (const key in arr) {
            if(key.includes(ars)){
                return true
            }else{
                return false
            }
        }
    }
    console.log(arrFn(9))
</script>